@scottsonline I agree something happened April 15, but it IS NOT related to the Boston marathon, because the drop happened worldwide (UK, Germany, Mexico, Colombia) and traffic is still low 3 weeks later.
Several people are seeing a decrease of 10%-30% starting April 15.
Some are seeing large fluctuations, starting also in mid April.
Some report large changes in traffic with and without changes in the SERP.
Some report large changes in direct and referral traffic in the same proportion as organic Google traffic.
Let's find out what it is and how to adjust.